A compact low temperature scanning tunneling microscope

Abstract

We describe the design and fabrication of a compact Low Temperature Scanning Tunneling Microscope (LT-STM) together with a dipper cryostat for cooling the STM down to liquid helium temperatures. The STM, based on the piezo-tube walker as coarse approach mechanism, is suspended inside a cryostat vacuum can using three soft helical springs. The can is dipped into a liquid helium storage container for cooling the STM. Its compact size makes it less susceptible to mechanical vibrations and so the STM works with atomic resolution with a simple spring suspension. We demonstrate the performance of this STM for atomic resolution imaging and tunneling spectroscopy by observing the 3 ×3 charge modulation and the energy gap in the Charge Density Wave (CDW) phase of 2H-NbSe2 at liquid helium temperatures.